EP2623031A1

EP2623031A1 - Tubular sensor, constituent measuring device, and tubular sensor manufacturing method

Info

Publication number: EP2623031A1
Application number: EP11828612.9A
Authority: EP
Inventors: Hideo Kawamoto
Original assignee: Terumo Corp
Current assignee: Terumo Corp
Priority date: 2010-09-30
Filing date: 2011-07-28
Publication date: 2013-08-07
Also published as: JP5758606B2; US20160345883A1; US9521972B2; JP2012075550A; CN103153188A; US20130225957A1; WO2012043051A1; HK1185776A1; US10188336B2; CN103153188B; EP2623031A4

Abstract

An objective of the present invention is to provide a tubular sensor capable of carrying out high-accuracy constituent detection and that is easy to manufacture, as well as a constituent measuring device and a method of manufacturing the tubular sensor. Accordingly, the present invention provides a tubular sensor including: a tubular body having a cavity extending through the tubular body in a longitudinal direction thereof; an insulation layer formed on an inner wall surface of the tubular body; and a plurality of electrodes formed on the insulation layer in the longitudinal direction of the tubular body, and extending continuously from one end to the other end of the tubular body. The present invention further provides a constituent measuring device which employs the tubular sensor. In addition, the tubular sensor is manufactured via the steps of: forming the insulation layer on a thin metal sheet; forming the plurality of electrodes on the insulation layer in stripes; cutting the thin metal sheet having the insulation layer and the electrodes formed thereon and forming a plate-shaped body which has a development shape of the tubular body having the cavity extending through the tubular body in the longitudinal direction thereof in a state in which the thin metal sheet and the plate-shaped boy are partially connected; and press working the plate-shaped body to form the tubular body.

Description

Technical Field

The present invention relates to a tubular sensor for detecting a constituent in a liquid such as body fluid, and a method of manufacturing the same. In addition, the invention relates to a constituent measuring device using the tubular sensor.

Background Art

Conventionally, for measurement of various constituents in body fluid, a method has been adopted in which measurement is conducted by use of specific enzymatic substances capable of reacting with specific constituents in the body fluid. Especially, measurement of blood glucose level is important for monitoring a patient's condition. Therefore, self-monitoring of blood glucose is recommended in which daily variation in blood glucose level is monitored by the patient himself or herself.
In the measurement, it is necessary, for example, for the patient to puncture the skin of the patient's finger or the like with a puncturing device having a puncture needle, to press the surroundings of the punctured part with a finger or the like to squeeze out blood, and to take the squeezed-out blood into a disposable sensor mounted to a measuring device. Therefore, this approach has had a problem as to workability.
In order to alleviate the complicatedness involved in the measurement work, in recent years, a device in which a sensor and a puncture needle are integrated has been proposed.
For instance, Patent Document 1 set forth below describes that two electrodes are arranged in a tubular puncture needle having a cavity therein. The electrodes in the puncture needle are connected to a control substrate through electric wires, and measurement of a current is conducted.
In this method, blood glucose level can be measured by using the blood sampled into the puncture needle. Therefore, the amount of blood needed for measurement can be reduced. In addition, after the patient's skin is punctured with the puncture needle, the measurement can be performed directly in that condition. This makes it possible to alleviate the burden on the patient.
Besides, Patent Document 2 set forth below describes that an oxygen fixation working electrode, a counter electrode and a reference electrode are arranged in a capillary tube connected to a minute injection needle. In this method, blood is guided into the capillary tube through the minute injection needle by capillarity, and an oxidation current is measured by the three electrodes in the capillary tube.
On the other hand, a method of manufacturing a tubular body having a cavity therein along its longitudinal direction, such as an injection needle, is proposed in Patent Document 3 set forth below. In the method described in Patent Document 3, first, a thin metal sheet is blanked into a development shape of the desired tubular body. Then, the thin sheet in the development shape of the tubular body is gradually rounded by press working, to mold it into a tubular shape.

Prior Art Documents

Patent Documents

Patent Document 1: Japanese Patent Laid-open No. 2007-54407
Patent Document 2: Japanese Patent Laid-open No. Hei 9-94231
Patent Document 3: Japanese Patent No. 3943390

Summary of Invention

Technical Problems

In the technique described in Patent Document 1, however, it is necessary, after separate production of a puncture needle and electrodes, to immobilize the electrodes in a minute space inside the puncture needle. Thus, this technique has problems in regard of immobilization accuracy and productivity.
In addition, for accurate detection of a current generated by an enzymatic reaction, it is desirable to keep the distance between the two electrodes constant. When there is unevenness in the immobilization accuracy of the electrodes as above-mentioned, however, dispersion in the inter-electrode distance is generated, making it impossible to perform a highly accurate constituent detection.
Besides, in the technique described in Patent Document 2, also, a working electrode, a counter electrode and a reference electrode which are formed in a small-diameter rod-like shape have to be inserted into a capillary tube. Since the three electrodes are immobilized in the cavity of the capillary tube, it is difficult to arrange the electrodes with high positional accuracy. Therefore, dispersion in inter-electrode distance is liable to be generated, possibly influencing the constituent detection accuracy.
In addition, two members consisting of the puncture needle and the capillary tube are needed, and a step of connecting them together is also needed, leading to a rise in manufacturing cost.
In consideration of the above-mentioned problems, it is an object of the present invention to provide a tubular sensor capable of a highly accurate constituent detection and capable of being manufactured easily, as well as a constituent measuring device and a method of manufacturing the tubular sensor.

Technical Solution

In order to solve the above-mentioned problems, a tubular sensor according to the present invention includes: a tubular body having a cavity extending through the tubular body in a longitudinal direction thereof; an insulation layer formed on an inner wall surface of the tubular body; and a plurality of electrodes formed on the insulation layer along the longitudinal direction of the tubular body and extending continuously from one end to the other end of the tubular body.
According to the tubular sensor of the present invention, the electrodes are formed over the inner wall surface of the tubular body, with the insulation layer therebetween. Therefore, the electrodes are immobilized onto the tubular body, so that an inter-electrode distance can be easily kept constant.
In addition, a constituent measuring device according to the present invention includes: the above-mentioned tubular sensor; a measuring unit configured to measure an electrical signal outputted by the tubular sensor; and a control unit configured to compute a detection signal obtained upon measurement at the measuring unit and to determine a value of a constituent in a liquid sampled into the tubular sensor.
The constituent measuring device according to the present invention is configured by use of the above-mentioned tubular sensor. Therefore, the electrodes are immobilized onto the tubular body, so that the inter-electrode distance is kept constant. As a result, an electrical signal according to the constituent of the liquid sampled into the tubular sensor can be detected with high accuracy.
Besides, a tubular sensor manufacturing method according to the present invention includes a step of forming an insulation layer on a thin metal sheet, and a step of forming a plurality of electrodes on the insulation layer in stripes.
In addition, the tubular sensor measuring method according to the present invention includes also a step of cutting the thin metal sheet formed with the insulation layer and the electrodes and forming a plate-shaped body in a shape of a development of a tubular body having a cavity extending through the tubular body in a longitudinal direction thereof, and a step of press working the plate-shaped body to form the tubular body.
According to the tubular sensor manufacturing method of the present invention, it is possible to easily produce the tubular body with the electrodes immobilized on the inner wall surface thereof. Therefore, it is possible to omit a process of separately producing a tubular body and electrodes, thereafter inserting the electrodes into the tubular body, and immobilizing the electrodes in the tubular body.
In addition, since the electrodes can be formed in the state of being immobilized over the inner wall surface of the tubular body, the inter-electrode distance can be kept constant.

Advantageous Effects

According to the tubular sensor of the present invention, the electrodes are immobilized on the inner wall surface of the tubular body, so that the inter-electrode distance is kept constant. Consequently, accurate current detection can be achieved.
In addition, according to the constituent measuring device of the present invention, the above-mentioned tubular sensor is used, whereby the electrical signal according to the constituent of the liquid sampled into the tubular sensor can be detected with high accuracy.
Besides, in the tubular sensor manufacturing method according to the present invention, it is possible to omit the process of separately producing the tubular body and electrodes, thereafter inserting the electrodes into the tubular body, and immobilizing the electrodes in the tubular body. Therefore, the manufacturing steps can be simplified, and a reduction in cost can be contrived.

Brief Description of Drawings

[FIG. 1]
FIG. 1A is a side view of a tubular sensor according to a first embodiment of the present invention, FIG. 1B is an illustration of the tubular sensor according to the first embodiment of the present invention, as viewed in a longitudinal direction of the tubular sensor, and FIG. 1C is a sectional view of the tubular sensor according to the first embodiment of the present invention.
[FIG. 2]
FIG. 2 is an illustration of a manner in which the tubular sensor according to the first embodiment of the present invention is connected to an external apparatus.
[FIG. 3]
FIG. 3A is an illustration of a tubular sensor in which outside diameter and inside diameter are varied stepwise, FIG. 3B is an illustration of a tubular sensor in which outside diameter and inside diameter are varied continuously, and FIG. 3C is an illustration of a tubular sensor in which outside diameter and inside diameter are constant.
[FIG. 4]
FIG. 4A is a top plan view of a thin metal sheet formed with an insulation layer and electrodes, as viewed from above, and FIG. 4B is a sectional view of the same.
[FIG. 5]
FIG. 5A is an illustration of a plate-shaped body formed by cutting a thin metal sheet, FIG. 5B is an illustration of a manner in which the plate-shaped body is press worked by use of an upper die and a lower die, FIG. 5C is an illustration of a condition in which the plate-shaped body is curved by press working, and FIG. 5D is an illustration of a manner in which the plate-shaped body is worked into a closed curved surface by use of another upper die to form a tubular body.
[FIG. 6]
FIG. 6 is a schematic sectional view of the upper die and the lower die for use in press working of the plate-shaped body.
[FIG. 7]
FIG. 7A is an illustration of electrodes arranged in a plate-shaped body to be molded into a tubular body having a constant diameter, and FIG. 7B is an illustration of electrodes arranged in a plate-shaped body to be molded into a tubular body whose diameter varies stepwise.
[FIG. 8]
FIG. 8A is an illustration of a case in which one of electrodes is located on a joint surface of a tubular body, and FIG. 8B is an illustration of a case in which one of electrodes is located on an inner wall surface of a tubular body at a position opposite to a joint surface of the tubular body.
[FIG. 9]
FIG. 9A is an illustration of a case in which four electrodes are disposed in a tubular body, and FIG. 9B is an illustration of a condition in which, of four electrodes disposed in a tubular body, two are located at parts which may be damaged.
[FIG. 10]
FIG. 10 is an illustration of a constituent measuring device according to a second embodiment of the present invention.

Modes for Carrying Out the Invention

Examples of the best mode for carrying out the present invention will be described below, but the invention is not to be restricted to the following embodiments. Description will be made in the following order.

1. First Embodiment
- 1-1. Tubular Sensor
- 1-2. Tubular Sensor Manufacturing Method
2. Second Embodiment
- 2-1. Constituent Measuring Device

1. First Embodiment

1-1. Tubular Sensor

FIG. 1A is a side view of a tubular sensor 100 according to a first embodiment. In addition, FIG. 1B is a view, taken along arrow A, of the tubular sensor 100 in FIG. 1A, and FIG. 1C is a sectional view of the tubular sensor 100 shown in FIG. 1A.
The tubular sensor 100 according to this embodiment includes a tubular body 1 having a cavity in a longitudinal direction thereof, an insulation layer 2 formed on an inner wall surface of the tubular body 1, and electrodes 3 formed on the insulation layer 2.
The tubular body 1 is formed, for example, of a metallic material. Examples of the metallic material include stainless steels such as SUS304, SUS316, etc., aluminum, aluminum alloys, and titanium. Other materials may also be used insofar as they are comparable to the just-mentioned metallic materials in hardness, ductility and plasticity.
The tubular body 1 has a hollow structure in which a cavity extends therethrough in the longitudinal direction thereof. Besides, here, the tubular body 1 is so shaped as to have different outside diameters and different inside diameters at both ends thereof.
In addition, the outside diameter and inside diameter of the tubular body 1 are not specifically restricted. In a case where the tubular body 1 is to be used as a puncture needle, the outside diameter of the tubular body 1 is, for example, 0.1 to 0.3 mm.
The length of the tubular body 1 is also not particularly limited. In the case of use as a puncture needle, however, the length is appropriately selected according to the puncture depth and strength required.
Besides, in the case where the tubular body 1 is to be used as a puncture needle, it may be formed with a cutting edge surface 4 at one end thereof.
The insulation layer 2 is formed on the inner wall surface of the tubular body 1. The insulation layer 2 is formed, for example, of an insulating plastic material. The plastic material is selected, for example, from a group consisting of polyvinyl chloride, polycarbonates, polysulfones, nylons, polyurethane, polyesters, acrylic resins, polystyrene and the like. Also usable are other non-conductive materials than plastic materials, such as cellulose.
In addition, the insulation layer 2 can be formed by various methods such as adhesion, welding, coating, printing, and semiconductor process.
On the insulation layer 2 are formed the electrodes 3, which extend in the longitudinal direction of the tubular body 1 continuously from one end to the other end of the tubular body 1. As will be described later, the electrodes 3 can be formed by printing, coating or the like while using an Ag paste, a carbon paste or the like. Besides, other materials may also be used insofar as they have conductivity suitable for use as electrodes, and the electrodes 3 may be formed by other semiconductor processes such as vapor deposition and sputtering.
In addition, the electrodes 3 are formed in the number of at least two. In FIG. 1B, an example in which two electrodes 3 are arranged is shown. In a case of measurement of blood glucose level, for example, the two electrodes 3 are used as a working electrode and a counter electrode, respectively. In a case where three or more electrodes 3 are formed, two electrodes are selected therefrom to be used as a working electrode and a counter electrode, respectively.
Where three or more electrodes 3 are formed, as will be described later, there is a merit that even when one of the electrodes 3 is troubled in the manufacturing process thereof, two electrodes selected from among the remaining electrodes can be used as a working electrode and a counter electrode, respectively.
On the electrodes 3, a reagent containing an enzyme such as glucose oxidase and glucose dehydrogenase is immobilized in a dry state. Glucose in blood sampled into the cavity of the tubular body 1 is oxidized by the enzyme, and a current arising from transfer of electrons through a mediator is detected by the electrodes 3.
As shown in FIG. 2, the electrodes 3 are connected to terminals 6 of a connection section 5 of, for example, a measuring instrument for measurement of this current. The terminals 6 are formed, for example, from a conductive rubber such as Zebra rubber. In addition, as indicated by arrows A1 and A2, the electrodes 3 of the tubular sensor 100 and the terminals 6 are made to correspond to each other and are connected to each other with position adjustment.
The terminals 6 may be formed from other material than the above-mentioned. The fashion of connection, such as shape, is not specifically restricted.
In the case of measurement of blood glucose level, for example, the tubular sensor 100 is made to puncture a patient's skin. Then, blood sampling may be carried out, with the tubular sensor 100 kept puncturing the skin. Alternatively, after the tubular sensor 100 is pulled out, the blood exuding onto the skin surface may be sampled. The blood is sampled into the cavity of the tubular body 1 by capillarity, for example.
Thus, in the tubular sensor 100 according to this embodiment, the electrodes 3 are immobilized on the inner wall surface of the tubular body 1 having the cavity along the longitudinal direction thereof. This ensures that it is easy to keep the inter-electrode distance between the working electrode and the counter electrode constant, and enhanced accuracy of measurement can be promised.
In addition, as the electrodes 3, there can be used electrodes which are formed by a semiconductor process, for example. This ensures that the tubular sensor 100 can be manufactured collectively, as will be described later. Accordingly, there is no need to insert electrodes into a cavity of a tubular body or to adhere the electrodes to the tubular body, after separately forming the tubular body and the electrodes. As a result, manufacturing steps can be simplified, and productivity can be enhanced.
Besides, in the case where the tubular sensor 100 is provided with the cutting edge surface 4, it is possible, after puncture of a patient's skin by the tubular sensor 100, to sample blood under that condition and to measure the blood glucose level or the like. Therefore, the amount of work can be reduced, and the burden on the patient can be alleviated accordingly. In addition, according to the present embodiment, the electrodes 3 are disposed in the cavity of the tubular body 1. Therefore, the measurement can be performed with a small amount of blood sampled into the cavity.
Here, an exemplary shape in which the outside diameter of the tubular body 1 has different values at both ends of the tubular body 1 has been mentioned. The shape, however, may be such that the outside diameter varies in three steps as shown in FIG. 3A, or may be such that the diameter varies continuously as shown in FIG. 3B. Further, the shape may be such that the outside diameter is constant as shown in FIG. 3C.
In addition, the cross-sectional shape of the tubular body 1 is not restricted to a true circle but may be a polygon, such as a tetragon and a hexagon, or may be an ellipse.

1-2. Tubular Sensor Manufacturing Method

Now, a method of manufacturing the tubular sensor 100 according to this embodiment will be described below, referring to FIGS. 4 to 9. The parts corresponding to those in FIG. 1 are denoted by the same reference symbols as used in FIG. 1.
FIG. 4 is a top plan view showing a condition where the insulation layer 2 and the electrodes 3 are respectively formed over a thin metal sheet 8, and FIG. 4B is a sectional view taken along line X-X' of FIG. 4A.
The thin metal sheet 8 is formed, for example, of a metallic material. Examples of the metallic material include stainless steels such as SUS304, SUS316, etc., aluminum, aluminum alloys, titanium, and titanium. Besides, other materials may also be used insofar as they are comparable to the just-mentioned materials in hardness, ductility and plasticity.
First, the insulation layer 2 is formed on the thin metal sheet 8. The insulation layer 2 is formed, for example, from an insulating plastic material. The plastic material is selected, for example, from a group consisting of polyvinyl chloride, polycarbonates, polysulfones, nylons, polyurethane, polyesters, acrylic resins, and polystyrene. Also usable are other non-conductive materials than plastics, such as cellulose.
In the case where the insulation layer 2 is formed from such an organic polymer material as just-mentioned, the insulation layer 2 can be formed, for example, by a coating method such as spin coating, or by a printing method such as screen printing. Besides, the insulation layer 2 may be formed by other method such as semiconductor processes, and adhesion or welding or the like techniques.
After the insulation layer 2 is formed on the thin metal sheet 8, the electrodes 3 are formed in stripes, for example. The electrodes 3 are formed, for example, from Ag, carbon or the like. Besides, other metals, alloys and conductive organic materials may also be used insofar as they have ductility and plasticity such that they can endure the subsequent press working.
Formation of the electrodes 3 can be conducted by a printing method using an Ag paste, a carbon paste or a solution containing other conductive substance.
In addition, in a case where the electrodes 3 are formed from a conductive inorganic material, a process may be employed in which a conductive film is formed by such a method as sputtering, vapor deposition or plating, and thereafter the conductive film is patterned by etching, lift-off or the like to form the electrodes 3.
Thus, in this embodiment, the electrodes 3 are preliminarily formed by a semiconductor process, in carrying out the manufacturing process. Therefore, unlike in the conventional process, there is no need to separately produce a puncture needle and electrodes, to insert the electrodes into the puncture needle, and to adhere the electrodes onto the puncture needle. Consequently, collective manufacturing through a series of processes is possible.
After the electrodes 3 are formed, shapes as if obtained by unfolding desired tubular bodies 1 are cut, as indicated by broken lines 9 and 10 in FIG. 4A, to form plate-shaped bodies. This cutting may be mechanical cutting by use of a press, or may be heat-aided cutting such as laser cutting.
In addition, here, the cutting is conducted through position adjustment such that two electrodes 3 are included in each of the development shapes indicated by the broken lines 9 and 10.
FIG. 5A shows the state after the cutting. By the cutting, plate-shaped bodies 11 having the development shapes of the desired tubular bodies 1 are formed. Besides, a plate-shaped body 11 is formed in a state of being connected to the thin metal sheet constituting frame parts 14 left in the surroundings thereof, through connection parts 12 and 13.
In addition, the connection parts 12 and 13 are provided on the longitudinal-directionally one end and other end of the tubular body when the plate-shaped body 11 is molded into the tubular body 1.
Next, as shown in FIG. 5B, the plate-shaped body 11 is press worked from upper and lower sides by use of an upper die 15 and a lower die 16, whereby the plate-shaped body 11 is gradually rounded through curving.
For instance, a projected die is used as the upper die 15 disposed on the upper side of the plate-shaped body 11, whereas a recessed die is used as the lower die 16 disposed on the lower side of the plate-shaped body 11.
Here, FIG. 6 shows a sectional view of the upper die 15 and the lower die 16. The lower die 16 has a shape provided with a step, as indicated by arrow A3. Accordingly, the press working is conducted while an end portion on a smaller diameter side of the tubular body to be formed is lifted up and displaced upward in relation to the frame part 14.
This ensures that, even in the case of the tubular body having different diameters at both ends thereof, an axis of the tubular body and the frame part 14 can be maintained in parallel to each other. Besides, in this case, the axis of the tubular body is located above the thin metal sheet surface of the frame part 14.
Returning to FIG. 5, as the press working is repeated gradually, the plate-shaped body 11 is curved into a U-shaped form as shown in FIG. 5C. In this process, the plate-shaped body 11 may be gradually curved by changing the sizes of the upper die 15 and the lower die 16, or may be curved while using the same upper and lower dies.
After the curving of the plate-shaped body 11 proceeds to the condition of FIG. 5C, pressing is conducted this time by use of a recessed upper die 18, as shown in FIG. 5D, and the plate-shaped body 11 is further curved into a closed curved surface. As a result, the tubular body 1 is formed.
In a case where a seam 19 in the tubular body 1 can be made liquid-tight by only the press working, cutting of the connection parts 12 and 13 results in that the tubular body 1 is cut off from the frame parts 14. The seam 19 of the plate-shaped body 11 may be joined to be liquid-tight by use of an adhesive or by welding or the like.
It is to be noted here, however, that joining by welding is preferably employed, since the tubular body 1 is formed from a metal and has a very small outside diameter. The method for welding is not specifically restricted. For instance, welding can be conducted employing carbon dioxide gas laser, YAG laser, excimer laser or the like.
With the tubular body 1 cut off from the frame parts 14, the tubular sensor 100 (see FIG. 1) in this embodiment is substantially completed. In the case of using the tubular sensor 100 as a puncture needle, the cutting edge surface 4 (see FIG. 1) is formed, for example, by subjecting a distal end of the tubular body 1 to cutting, grinding, and polishing or the like.
Besides, in the case of using the tubular sensor 100 as a sensor for measurement of blood glucose level or the like, a reagent containing an oxidoreductase is applied onto the electrodes 3 before cutting-out of the plate-shaped body 11. Or, alternatively, a process may be adopted in which the tubular body 1 is formed and cut off from the frame parts 14, and thereafter the distal end of the tubular body 1 is immersed in a liquid reagent to deposit the reagent on the electrodes 3.
While an example in which two electrodes are arranged in the tubular body has been described here, three or more electrodes may be arranged. In that case, it suffices to conduct arrangement of the electrodes 3 and cutting so that three electrodes are included in the plate-shaped body.
For instance, in the case of forming a tubular body with an outside diameter being constant along the longitudinal direction thereof, it suffices to conduct the cutting so that three electrodes 3 are included in the plate-shaped body in the development shape as indicated by broken line 20 in FIG. 7A.
Besides, in the case of forming a tubular body with its outside diameter having different values at both ends thereof as shown in FIG. 7B, it suffices to conduct the cutting so that three electrodes are included in the plate-shaped body in the development shape as indicated by broken line 21 in FIG. 7B.
It should be noted here, however, that in the plate-shaped body indicated by broken line 21 in FIG. 7B, three electrodes are arranged at an end portion on the side of smaller diameter after press working, whereas five electrodes are arranged at an end portion on the larger diameter side.
In the tubular body formed from the plate-shaped body with this shape, if blood sampled via the small diameter side end portion reaches electrodes 3a and 3b, these electrodes can be used for measurement of blood glucose level. Taking assuredness of blood sampling into account, however, it is preferable to select measuring and counter electrodes from among electrodes 3c arranged to extend up to the end portion on the small diameter side.
Such a configuration in which three or more electrodes are arranged in the plate-shaped body ensures that even if one of the electrodes is damaged during press working or welding, the remaining electrodes can be put to use as a working electrode and a counter electrode.
For instance, in FIG. 8A, three electrodes 3d, 3e and 3f are formed over the inner wall surface of the tubular body 1, with the insulation layer 2 therebetween. However, the electrode 3d arranged near a joint surface 22 joined by press working or welding may have been damaged by the welding heat. In such a case, by using the electrodes 3e and 3f as a working electrode and a counter electrode, a current can be measured assuredly.
Besides, in FIG. 8B, an electrode 3h is formed at a position opposite to the joint surface 22. The electrode formed in this position may have been damaged under a pressure exerted from the upper die 15 (see FIG. 5B) during press working.
In this case, therefore, by using electrodes 3g and 3k as a working electrode and a counter electrode, it is possible to obviate generation of an error in the measured value of current.
Further, FIG. 9 shows cases where four electrodes are arranged in the tubular body 1, with the insulation layer 2 therebetween.
In FIG. 9A, four electrodes 31, 3m, 3n and 3p are arranged inside the tubular body 1. However, the positions where the electrodes are arranged are deviated from the joint surface 22 of the tubular body 1 and from that position on the inner wall surface of the tubular body 1 which is opposite to the joint surface 22.
In this case, therefore, none of the electrodes 31, 3m, 3n and 3p has been damaged. Accordingly, arbitrary two of the electrodes can be selected for use as a working electrode and a counter electrode.
On the other hand, in FIG. 9B, of four electrodes 3q, 3r, 3s and 3t arranged, the electrode 3t is located near the joint surface 22 of the tubular body 1, and the electrode 3r is located at that position on the inner wall surface of the tubular body 1 which is opposite to the joint surface 22.
The electrode 3t may have been damaged during welding of the joint surface 22. The electrode 3r may have been damaged under the pressure exerted during press working.
In this case, therefore, by selecting the electrodes 3q and 3s for use as a working electrode and a counter electrode, a current can be measured in an assured manner.
Thus, by arranging three or more electrodes in the tubular body at regular intervals, it is possible to obviate a situation in which a damaged electrode might be used as a working electrode or a counter electrode.
In addition, it has been found that the parts where an electrode may be damaged are two positions, one of which is a position near the joint surface of the tubular body and the other of which is a position, opposite to the joint surface of the tubular body, on the inner wall surface of the tubular body. Accordingly, when four or more electrodes are arranged in one plate-shaped body at regular intervals, two or more electrodes are necessarily present in the state of being free of damage, so that these electrodes can be put to use as a working electrode and a counter electrode.
Besides, in the case where the electrodes are arranged at regular intervals as shown in FIG. 7, it is possible to leave, without fail, not less than a predetermined number of electrodes on the plate-shaped body, even if the plate-shaped body is cut at random without performing any position adjustment.
Therefore, it is preferable to form electrodes at regular intervals by setting an inter-electrode distance so that three or more electrodes are left in the plate-shaped body. Accordingly, by cutting the plate-shaped body at random in a direction orthogonal to the longitudinal axis thereof, it is ensured that even an electrode is arranged near the joint surface of the tubular body or at a position where a pressure is exerted during press working and is damaged, the remaining electrodes can be put to use as a working electrode and a counter electrode.
In other words, a positioning process can be omitted at the time of cutting, so that enhanced productivity is promised and the manufacturing cost can be lowered.

2. Second Embodiment

2-1. Constituent Measuring Device

As a second embodiment, an example of configuring a constituent measuring device for measurement of blood glucose level by use of the above-described tubular sensor 100 will be described.
FIG. 10 is a schematic block diagram showing a configuration of a constituent measuring device 200 according to the second embodiment. The constituent measuring device 200 according to this embodiment includes, for example, a blood sampling chip 30 configured to sample blood and generate an electrical signal according to the amount of glucose in the blood thus sampled, and a measuring unit 60 configured to measure the electrical signal generated in the blood sampling chip 30.
In addition, the constituent measuring device 200 according to this embodiment further includes a control unit 70 configured to compute a detection signal obtained upon measurement by the measuring unit 60 and determine the blood glucose level of the blood sampled, and a display unit 80 configured to display the blood glucose level computed in the control unit 70.
The blood sampling chip 30 includes a puncture needle unit 40, and a housing 50 for holding the puncture needle unit 40. The housing 50 is provided with a cavity 51 extending therethrough along a longitudinal direction thereof, and the puncture needle unit 40 is held in the cavity.
The puncture needle unit 40 includes the tubular sensor 100 disposed at a distal end thereof, a hub 41 for holding the tubular sensor 100, a gripped section 42 connected and secured to a rear stage of the hub 41, and a pair of wires 45.
This tubular sensor 100 is the one which has been shown in the first embodiment (see FIG. 1), and the inside diameter of a distal portion thereof is so small that blood can be guided into the tubular sensor 100 by capillarity. In addition, the tubular sensor 100 has its rear end portion held in the hub 41.
Besides, the gripped section 42 is connected and secured to the rear stage of the hub 41, and the tubular sensor 100 and the gripped section 42 are in contact with each other in the cavity in the hub 41.
In addition, the cavity in the tubular sensor 100 communicates rearward through a vent hole 42a and a central hole 42b provided in the gripped section 42.
Besides, the gripped section 42 is gripped by a gripping section 43. An urging bar 44 disposed inside the gripping section 43 urges the puncture needle unit 40 through the gripping section 43 by urging means (not shown). As a result, the cutting edge surface of the tubular sensor 100 is moved into and out of the housing 50.
The electrodes in the tubular sensor 100 are connected to the wires 45. The wires 45 are so set, for example, as to pass through the vent hole 42a of the gripped section 42, and thereafter penetrate to an outer surface of the gripped section 42, whereon they are extended on the outer surface of the gripped section 42.
On the other hand, on an inner surface of the gripping section 43 for gripping the gripped section 42, a pair of terminal wires 46 which make contact with the wires 45 are provided. The terminal wires 46 are connected to the measuring unit 60 configured to measure the signal from the tubular sensor 100.
The measuring unit 60 includes a power supply 63, a voltage changing circuit 61 configured to change a voltage supplied from the power supply 63 and impress the thus changed voltage on the electrodes of the tubular sensor 100, and a current measuring section 62 configured to measure a current generated according to the amount of a constituent in a liquid sampled into the tubular sensor 100.
A predetermined voltage is impressed between the electrodes in the tubular sensor 100 by the voltage changing circuit 61, whereby a current according to the amount of glucose in blood is made to flow through the current measuring section. The change in the current is measured by the current measuring section 62, which outputs a detection signal to the control unit 70.
The control unit 70 computes blood glucose level by a computation treatment based on the detection signal inputted thereto and while performing, if required, a corrective computation. The blood glucose level thus computed is outputted to and displayed on the display unit 80, for example.
Thus, in the constituent measuring device 200 according to this embodiment, the tubular sensor 100 shown in the first embodiment is used. In the tubular sensor 100, the electrodes are secured to the inner wall surface thereof, so that the inter-electrode distance is securely kept at a constant value. Accordingly, measurement of blood glucose level, for example, can be performed with high accuracy.
In measuring a patient's blood glucose level, first, the patient's skin is instantaneously punctured by the tubular sensor 100. Next, while using the tubular sensor 100 as it is, blood is sampled into the tubular sensor 100 from a minute blood lump 90 generated in the cavity 51, whereby measurement of the blood glucose level can be performed. In other words, the blood glucose level measurement can be carried out by a highly simplified operation. Consequently, the burden on the patient can be lightened.
In addition, the blood glucose level measurement can be carried out by use of only the blood sampled into the tubular sensor 100. Therefore, the amount of blood necessary for the measurement can be made small. Especially, in the case where use is made of the tubular body 1 having different diameters at one end and the other end thereof, the blood sampled via the smaller diameter part side would not easily enter a larger diameter part side due to capillarity. This promises a further reduction in the amount of blood to be sampled.
Besides, when a reagent is placed only in the smaller diameter part on the distal side of the tubular sensor 100, a further reduction in the amount of blood to be sampled can be achieved, which naturally is preferable. The insulation layer 2 formed on the inner wall surface of the tubular sensor 100 is formed of a plastic material and, therefore, is hydrophobic. On the other hand, the reagent is hydrophilic. Therefore, blood is sampled only into a region where the reagent is applied. Accordingly, the measurement can be performed by use of only the blood sampled into the smaller diameter part coated with the reagent, for example. Consequently, the amount of blood to be sampled can be reduced more assuredly.
Some embodiments of the tubular sensor, the constituent measuring device, and the tubular sensor manufacturing method according to the present invention have been described above. The present invention is not restricted to the above embodiments, and various modes are embraced in the present invention insofar as they are within the scope of the invention as defined by the claims.
Besides, while an example of measuring blood glucose level in blood has been shown here, the tubular sensor according to the present invention can be used, for example, as a sensor for measurement of the sugar content of a fruit or vegetable, or as a sensor for measurement of a chemical constituent of river water or industrial liquid waste.

Explanation of Reference Symbols

1 ... Tubular body, 2 ... Insulation layer, 3, 3a, 3b, 3c, 3d, 3e, 3f, 3g, 3h, 3k, 31, 3m, 3m, 3p, 3q, 3r, 3s, 3t ... Electrode, 4 ... Cutting edge surface, 5 ... Connection section, 6, 46 ... Terminal, 8 ... Thin metal sheet, 9, 10, 20, 21 ... Line, 11 ... Plate-shaped body, 12, 13 ... Connection part, 14 ... Frame part, 15, 18 ... Upper die, 16 ... Lower die, 19 ... Seam, 22 ... Seam, 30 ... Blood sampling chip, 40 ... Puncture needle unit, 41 ... Hub, 42 ... Gripped section, 42a ... Vent hole, 42b ... Central hole, 43 ... Gripping section, 44 ... Urging bar, 45 ... Wire, 46 ... Terminal wire, 50 ... Housing, 51 ... Cavity, 60 ... Measuring unit, 61 ...
Voltage changing circuit, 62 ... Current measuring section, 63 ... Power supply, 70 ... Control unit, 80 ... Display unit, 90 ... Blood lump, 100 ... Tubular sensor, 200 ... Constituent measuring device

Claims

A tubular sensor comprising:
a tubular body having a cavity extending through the tubular body in a longitudinal direction thereof;

an insulation layer formed on an inner wall surface of the tubular body; and

a plurality of electrodes formed on the insulation layer along the longitudinal direction of the tubular body and extending continuously from one end to the other end of the tubular body.
The tubular sensor according to claim 1,
wherein the plurality of electrodes are formed on the inner wall surface of the tubular body in the number of at least three.
The tubular sensor according to claim 2,
wherein the at least three electrodes are formed at regular intervals along a circumferential direction of an inner wall of the tubular body.
The tubular sensor according to any one of claims 1 to 3, wherein a cutting edge surface is provided at a distal end of the tubular body.
A constituent measuring device comprising:
the tubular sensor according to any one of claims 1 to 4;

a measuring unit configured to measure an electrical signal outputted by the tubular sensor; and

a control unit configured to compute a detection signal obtained upon measurement at the measuring unit and to determine a value of a constituent in a liquid sampled into the tubular sensor.
A tubular sensor manufacturing method comprising:
a step of forming an insulation layer on a thin metal sheet;

a step of forming a plurality of electrodes on the insulation layer in stripes;

a step of cutting the thin metal sheet formed with the insulation layer and the electrodes and forming a plate-shaped body in a shape of a development of a tubular body having a cavity extending through the tubular body in a longitudinal direction thereof; and

a step of press working the plate-shaped body to form the tubular body.
The tubular sensor manufacturing method according to claim 6, wherein the plate-shaped body is so cut that a longitudinal direction of the electrodes coincides with the longitudinal direction of the tubular body.
The tubular sensor manufacturing method according to claim 6 or 7, comprising
a step of welding a seam of the tubular body obtained by the press working.
The tubular sensor manufacturing method according to any one of claims 6 to 8, wherein the plate-shaped body is formed in a state of being partially connected to a frame part left in the thin metal sheet in a frame shape.
The tubular sensor manufacturing method according to any one of claims 6 to 9, wherein the plurality of electrodes are disposed at regular intervals.
The tubular sensor manufacturing method according to claim 10, wherein the thin metal sheet is cut so as to leave at least three of the electrodes on the plate-shaped body.